Piston



May 24, 1960 H. u. GARRETT ET AL 2,937,909

PISTON 4 Sheets-Sheet 1 Filed March 24, 1958 Henry U. Gar/"eff Norma/7 5 Brown INVENTORS BY W ATTO/F/VEVJ May 24, 1960 Filed March 24, 1958 H. U. GARRETT ET AL PISTON 4 Sheets-Sheet 2 ATTORNf/J May 24, 1960 H. u. GARRETT ET AL 2,937,909

PISTON 4 Sheets-Sheet 3 Filed March 24, 1958 6/ Gr/"e ff Hen "9 Nor/770 F [frown A TTOR/VEVJ Max 24, 1960 H. U. GARRETT ET AL 2,937,909

PISTON FiledMarch 24, 1958 4 Sheets-Sheet 4 Ill Henry (J Gar/eff Norma/7 /T 5/0 w/v INVENTORS ATTORNEYS United States Patent PISTON Henry U. Garrett and NormanF. Brown, Longview, Tex., assignors to US. Industries, Inc.,. New York, N.Y., a corporation of Delaware Filed Mar. 24, 1958, Ser. No. 723,513

17 Claims. (Cl. 309-33) The present invention relates to pistons which are to move rapidly through a pipe or the like. More particu. larly, the invention relates to such pistons having packers of the type made up of multiple intermeshing metallic segments and which are suitable for use as free pistons employed in the production of liquids from wells.

Free pistons have heretofore been developed for use in the production of oil and gas wells. It is desirable to lift oil, condensate, or water from wells by introducing gas under pressure beneath the liquids. The free piston is used to keep the liquid and gas from mixing at their interface. One successful form of sealing means between the pisto'n body and well tubing. or the like comprises a series of meshed metallic segments which are constantly resiliently and collectively urged radially outward from the body of the piston to seal between the tubing and piston body. The piston of this. invention may be. so used and in addition may be used-for such purposes as parafiin scraping and chemical injection.

The prior application for U.S. patent Serial No. 620,533, filed November 5, 1956, by Norman F. Brown, discloses a packer of the above-described general nature, having. elongated metallic segments which are urged radially outwardly by the force of a spring acting longitudinally of the segments. A wedging engagement between the inner surface of each of the segments and a ring sealed to the body directs the outer surface of each of the segments radially outward into contact with the pipe wall as they are moved longitudinally by the spring. Each segment has one end mounted to pivot and move longitudinally with respect to the body and the segments pivot from their ends as they follow the wedge surfaces. The segments also have mutually engaging lateral wedge cam surfaces which cooperate to maintain a seal between the segments over the range of their radial movement and their collective circumferential expansion.

The packer of the said Brown application is very efiicient in maintaining the required sliding seal with tubing through which the piston is moved. The packer conforms to the tubing, maintaining an eifective seal, even though the tubing goes out of round. However, as the segments pivot about their ends in moving their tubing engaging surfaces radially in and out, their tubing engaging surfaces wear to an arc shape. When so worn these surfaces contact the tubing substantially along a line which extends circumferentially of the pipe instead of over a surface which extends a substantial distance along the length of the pipe. With such line contact, these segments wear rapidly, and also tend to enter the space between the tubing ends at each collar and then to be thrown rapidly back inwardly as they move past such space, such rapid inward and outward movement damaging them and damaging the packer as a whole so as. to substantially shorten the life of the packer and lessen its effectiveness;

' A principal object of the present invention is to provide a multiple segment type of packer in which the segments will have a greater life than in the packer just described.

A further object of the present invention. is to provide a multiple segment type of packer in which each segment will have at all times a large area of considerable longi tudinal extent in contact with the tubing wall so that each segment will be positioned against the pipe wall with low unit loading over its surface.

Another object of the invention is to greatly reduce or practically eliminate radial" acceleration forces on intermeshing packer segments due to their engagement. with the gaps between the pipe ends at collars.

Another objects is to provide an arrangement, in which each segment is urged bodily radially outwardly to cause it to engage the tubing over a substantial portion of its length, and in which alternate segments are urged at the same time in opposite longitudinal directions to keep them in contact with each other.

Still another object is to provide anarrangement in which such segments are urged resiliently ina radially outward direction and in a direction to keep themin contact'with-each, other, while making it possible to provide such resilient urging means in a way to enable it to exert a constant expansive force with little variation between the minimum and maximum radial po'sitions of the segments.

Other objects, features and advantages of the invention will be apparent from the drawings, the specifications and the claims. In the following description and the accompanying drawings there is set forth by way of'illustration and example one specific embodiment of this invention.

In the drawings:

Fig. 1 is a sectional view through a well' equipped'for gas lift production with a free piston constructed in accordance with this invention shown in elevation in the lubricator of the Christmas tree;

Fig. 2 is a view in longitudinal cross-section alongthe line 22 of Fig. 3 through one form of one of the packers of a free piston constructed in accordance with this invention;

Fig. 3 is a transverse cross-section taken along, the line 33 of Fig. 2';

Fig. 4 is a transverse cross-section taken along the line 44 of Fig. 2;

Fig. 5 shows a side elevation of a packer constructed in accordance with this invention with the segment retainingrings removed from the ends thereof for purpose of illustration;

Fig. 6 is a schematic fragmentary inside view of the apparatus shown in Figs. 2, 3 and 4;

Fig. 7 is an elevational view of one of the segments of the apparatus shown in Figs. 2, 3 and 4 taken from the inside of the apparatus; and

Fig. 8 is a view similar to Fig. 2 but showing a modification in which the expanding force is applied to each segment at a single point only.

In general, the objects of this invention are accomplished by providing packer segments with outer surfaces ofvery substantial longitudinal extent shaped to conform to the inner surface of a tubing or pipe in which the piston is adapted to operate, and then mounting the segments so that each segment may move bodily outwardly in all of its parts to permit the entire surface which is shaped to conform to the interior of the tubing to fully engage the interior of the tubing in which the piston is operating, together with a means for urging the segments outwardly with a substantially constant radial force. Such means may apply its outward forces at a plurality of longitudinally spaced points in each segment. Provision may be made in the latter case for balancingthe forces appliedat the two separate points of eachsegment against each other so that the segments will not be urged more strongly against the interior of a pipe at one portion of the length than at another. Likewise, provision is made for moving alternate segments lengthwise with respect to the other alternate segments simul taneously with expanding the same, and for balancing the forces expanding the two sets of alternate segments against each other so that the two sets of alternate segments will be expanded with substantially the same forces and will be simultaneously moved longitudinally with respect to each other so as to keep them in contact with each other throughout their circumferential extent as they are moved outwardly toward a pipe wall.

Referring first to Fig. 1, there is shown a free piston installation employing a free piston having a packer construction in accordance with this invention. At the top of a well employing such a free piston installation a lubricator is usually employed and is here indicated by the numeral 1. This lubricator is for use in the insertion and removal of the free piston. A latch mechanism 2 is provided in this lubricator for holding the free piston in its upper position at one stage of its operation. During normal operation this latching mechanism is positioned out of the way so that it is inoperative. It may be moved into operative position at any time it is desired to catch and hold the piston, as at the time just after it has been put into the lubricator or just before it is taken out.

Fluid raised by the free piston is intended to leave the well through the outlet 3, reaching this outlet through holes 4 and 5 in the lubricator which lead from the central passageway of the lubricator into a laterally disposed channel communicating with the outlet 3.

In operation the free piston is allowed to move downwardly through fluid in the well tubing 5 until it strikes a stop 6 carried by a resilient member 7 in the lower portion of the tubing, and in striking this stop 6 a mechanism not shown is actuated within the free piston to close the passageway therethrough. Gas is then admitted through a gas lift valve 8 into the interior of the tubing below the stop 6 and flows upwardly through the passageway 9 and this stop, collecting beneath the free piston and forcing the free piston upwardly together with the fluid through which the free piston has passed on its downward travel. Thus it lifts the fluid above the free piston and as the free piston approaches the upper end of the well this fluid is forced outwardly through the openings 4 and 5 and the outlet 3.

When the piston reaches the top of its travel it strikes the resiliently mounted stop 10 which absorbs the shock of the upwardly traveling piston and actuates a mechanism for opening a passageway through the piston and bypassing well fluid through the piston.

After the piston bypass is open, the piston drops back into the well passing through the fluid accumulation therein until it reaches again the resiliently mounted stop 6 in the bottom of the well. Thereupon it strikes this stop, the bypass valve is closed, and the process is repeated.

The present invention provides a means for packing around the free piston just described. It is also useful for such other purposes as a paraffin scraper, for the re moval of condensate, and in connection with chemical injection. It will be obvious that still other uses for this type of piston packer may be found.

Referring now to Figs. 2 to 7, inclusive, one form of the piston packer itself will be described in detail.

The piston packer in this instance is mounted on the body 11 of the free piston but it will be understood that when used for pistons or scrapers having a different function, the body or mandrel 11 may take some different form, though preferably externally it will be substantially cylindrical as it is in the present instance.

Surrounding this body at an intermediate point is a double wedge ring 12 mounted to move axially in either direction along the piston body and provided with a seal to the piston body by suitable means such as an O-ring 13. On its external surfaces this double wedge ring has oppositely inclined surfaces tapering outwardly as shown at 14 and 15, respectively.

Spaced axially in either direction on the body 11 from the double wedge ring 12 is an abutment ring, these being numbered 16 and 17, respectively. Each of these is mounted against a stop, these being 18 and 19, respectively, these stops preventing the abutment rings 16 and 17 from moving toward each other or toward the double wedge ring 12. Except for the stop rings 18 and 19 which are engaged within grooves in the outer surface of the body 11, the abutment rings 16 and 17 are'free to move axially on the body 11. Each of these abutment rings provides a shoulder to receive one end of a compression spring, one of these springs'being 20 and the other 21, so that the abutment rings 16 and 17 and the stop rings 18 and 19 taken together provide abutment anchors for the adjacent ends of the springs 20 and 21, respectively. Thereby these springs are enabled when compressed to exert forces in opposite directions from each other and away from the floating wedge ring 12. In order to con-fine the ends of the springs received therein respectively, these abutment rings 16 and 17 have axially directed flanges 22 and 23, respectively, embracing the ends of the respective springs 20 and 21.

The opposite ends of the springs 20 and 21 are like wise received by abutment rings 24 and 25, respectively, which, for the sake of convenience of manufacture and possible replacement, are made identical with each other in this instance. These second abutment rings are axial -ly movable on the body 11 and, like the abutment rings 16 and 17, have outer axially extending skirts 26 and 27, respectively, engaging about the outer ends of the springs 20 and 21. Each of these abutment rings 24 and 25 also provides on its surface most remote from the double wedge ring 12 a wedge surface which flares outwardly and toward the double wedge ring, as shown at 28 and 29, respectively. These wedge surfaces 28 and 29 make the abutment rings 24 and 25 into effectively single wedge rings for a purpose presently to be described.

Disposed about the exterior of the structure just described and extending along the body 11 beyond the extremities of the abutment rings 24 and 25 are a plurality of packet segments which are of such dimensions and number that taken together they completely encompass the body and the structure just described and abut each other to form a complete enclosure thereabout. These segments are preferably as illustrated all of identical construction although it is conceivable that they might be made dissimilar from each other so long as they are so constructed that they will engage each other to completely encircle the structure illustrated at all times While being expanded and contracted in accordance with this invention as hereinafter described. The essential features which must be incorporated in these segments even though they may be designed to be dissimilar will appear from the following description.

Each of these segments is provided with an exterior surface 30 which is substantially cylindrical and adapted to engage and fit substantially throughout its extent with the inner surface of a tubing or pipe or the like in which this invention is to be employed. Particularly it is contemplates that these segments will under no circumstances be required by their mounting and actuating mechanism to be cocked or til-ted from end to end so that these surfaces 30 will fail to engage the inner surface of the pipe or the like throughout the length of the surface 30. Thus, wear will be evenly distributed over the surface 39, and because of its large extent, particularly in an axial direction, it will move past collars and joints in the pipe without substantial radially inward and outward movement, and will have a low unit bearing force against the pipe so as to minimize wear on both the pipe and the segments.

. Each segment is provided on each of its two ends with a short endwise projection providingits axial extremities. These endwise projections 31 and 32 on the respective ends of the segments are substantially identical with each other and are adapted to provide inner surfaces which extend inwardly as far as any portion of the segment and are adapted when forced inwardly into engagement with the outer surface of the body 11 to provide a lim-t stop for inward movement of the segment ends, respectively.

These axial extensions 31 and 32 are also of small radial extent and are adapted to underlie skirt portions 33 and 34 of segment retaining rings 35 and 36, respectively, surrounding and secured to the body 11 at the opposite ends of the-packer segment assembly. These rings have parts spaced beyond. the ends of the packer segments snugly embracing the exterior of the body 11 and held against both axial and rotative movement on the body by means of dowel pins 37 inserted in holes 38 radially extending through. the retainer rings 35 and 36, and thence projecting into dowel holes 39 formed in the outer surface of the body 11 and adapted to register with the holes 38. These dowel pins may be retained in position in any suitable manner as by wires 40 extended about the exterior of the retainer rings in grooves provided for the purpose, these grooves being in a plane substantially centered over the holes 38 so that when the wires 40 are put in place and tied they will extend across the tops of all of the dowel pins 37 for a given retainer ring thereby retaining those dowel pins in place.

The retainer rings have their skirts 34 spaced far enough away from the adjacent surface of the body 11 to permit the-projections 31 and 32, respectively, on the segments to move outwardly in a radial direction far enough topermit all of the outer surfaces 30 of the segments to engage the pipe or the like in which the device is intended to operate. Thus, each segment has free radially inward and outward movement within the limits necessary for the. operation of the device but each is retained in place by the retainer rings 35 and 36, respectively.

Furthermore, the retainer rings 35 and 36 are placed far enough apart so that the segments may move in an axial or longitudinal direction with respect to the body 11 sufliciently to enable them to expand and contract and maintain their circumferentialengagement with one another as will be hereinafter explained.

Further describing the individual segments, it will be seen that each is provided with an outwardly offset part adjacent the end extensions 31 and 32 so as to provide endwise facing shoulders 41 and 42,.respectively, on each segment directly opposed to the ends of the skirts 33 and 34 on the retainer rings 35 and 36. Each segment is also tapered from each of these shoulders for a short distance toward the midpoint ofthe segment, to provide a sled-runner effect in the form of a tapered portion 43 adjacent one end of the segment and 44 adjacent the other. This makes it impossible for the ends of the surface 30 to catch on small projections in the pipe or at the joints thereof.

Intermediate its ends each segment is provided on the inner face thereof with a hollowed out or recessed portion adapted to bridge over and in effect provide a housing for the double wedge ring, the abutment rings, and the springs hereinbefore described. At one end of this hollowed out portion each segment is provided with a single wedge surface 45 adapted to engage the wedge surface of the single wedge ring 24 or 25 as the case may be, and upon relative endwise movement of such single wedge ring toward the adjacent end of the segment, to cause an outward wedging action providing an outwardly directed radial force upon the segment at this point.

At its oppositerendfrom the single wedge surface 45,

each segment is provided with arecess longi'enoughto' extend over and completely clear. the opposite single wedge abutment ring 24 or. 25.

Each segment is provided with a second inwardly extending wedge surface 46 positioned so as to engage the double wedge ring on its face most remote from the surface 45. The arrangement is suchthat if the space between the single wedge ring in contact with the wedge surface 45 and the double wedge ring in contact with the wedge surface 46 be moved relatively farther apart, the result will be two radially outward forces exerted upon the segment at points substantially in the positions of the two Wedge rings mentioned. Thus, if the doublewedgering 12 be held against axial movement with respect to the body 11, and the spring 21, for example, is in a state-of compression urging the ring 25 in a direction away from the double wedge ring 12, then this ring25; having its surface 29 bearing against the wedge surface 45 of the segment, will produce the'same effect as though the two wedge rings were both moved. along the body 11 away from each other, andthe segmentwhich they engage will be urged radially outwardly with force applied at points determined by the double wedge ring and the single wedge ring acting on that segment, respectively. Preferably the bearing surface 30' of each segment extends substantially the entire length of the segment as illustrated in the drawings. However, it is essential that a sufficient portion of it lie between and adjacent the points of application of the forces by the double wedge ring 12 and the single wedge ring 24 or 25 so that the forces applied at these points will not tend to cock the segment one way or the other and move one end or the other of the surface 30 away from its engagement with the pipe or the like.

At this point, it should be stated that'the number of segments should be an even number and" they should be alternately oppositely disposed about the body 11 so that whereas one segment will have its surface 45in engage ment with the wedging surface 29 of' the ring 25, the next adjacent segments will have their surfaces 45 in engagement with the surface 28 of the wedge ring24. Also, it will appear that with this arrangement the spring2'1 will act on one-half of the segments, being alternate segments as disposed around the body, tending to expand them by forces applied at the locations of the-wedge ring 25 and the double wedge ring 12, whereasthe. other alternate segments will be acteduponby the spring 20 to produce expansive forces at the locations of the single wedge ring 24 and the double-wedge ring 12. Inasmuch as the same spring provides both radially directed forces acting upon a single segment, it will be apparent that these forces for each segment will be balanced against each other and whereas they may be unequalas related to each other, they will. always bear the same relationship to each other, this relationship being determined by the angle of inclination. of the wedging engagement of the respective wedge rings withthe wedging surfaces in the segments. It will further be apparent that inasmuch as the double wedge ring, 12 is mounted on the body 11 so as to be free for axial movement thereon, it will be enabled to'exert its wedging function only by virtue of the fact that alternate ones. of the segmentswill be expanded by engagement with the wedging surface on one side of this ring whereas the other alternate ones of the segments will be expanded by engagement with the wedging surface on the other side thereof; Thus the wedging forces on. the two sets of segments will be balanced against each other and the radially outwardly directed forces on these two setsof segments respectively will likewise be balanced in this fashion.

Inasmuch as the expansive forces acting on the respective'sets of alternate segments are applied to opposite sides of the double wedge ring 12, this doublewedgering will not move substantially in either. axial directiombut each 7 segment will be moved axially in a direction toward that end in which its single wedge surface 45 is located, as it .moves radially outwardly. Thus half of the segments asthey are moved radially outwardly will move axially in one direction, whereas the other half, alternately disposed between the first half, will be moved axially in the opposite direction.

Referring now to Figs. 5, 6 and 7, it will be seen that the intermediateportion of each segment is provided with lateral faces forming a wedge shape when taken together, so that this intermediate portion tapers toward one end of the segment. With the segments alternately disposed, these intermediate portions on alternate segments will be tapered in opposite directions. However, they will be so tapered as to fit together as illustrated quite clearly in Fig. 5. Furthermore, these intermediate portions not only taper in an axial direction but also in a radial direction. Thus, in transverse cross-section along the apex of the double wedge ring, for example, they would each appear to be pie-shaped with the point of the piece of pie cut off. This is quite clear from Figs. 6 and 7. The relationship of the angles of these lateral wedge faces which are designated 47 on upwardly tapering and 48 on downwardly tapering portions, respective ly, and the angles on the double wedge ring and wedging surfaces 46, and on the single wedge rings 24 and 25 and the single wedge faces 45, is such that for any given outward radial movement of a segment opposite the double wedge ring, there will also be an endwise movement of this segment with respect to the adjacent segments such as to maintain the lateral wedge faces 47 and 48 in engagement with each other from the outer surface 39 at least to the apex of the double wedge ring 12. Thus, the segments taken together will form a complete closure between the inner surface of the pipe or the like in which the device is being operated and the apex of the double wedge ring 12, and this double wedge ring 12 being sealed to the exterior of the body 11 by means such as the 'O-ring 13, there will be formed a complete closure between the interior of the pipe or the like in which the device is operating and the exterior of the body 11 and this will be true for all of the permissible degrees of expansion of the packer segments.

However, it will be appreciated that the surface 30 which is adapted to engage and shaped to fully engage with the adjacent wall of a pipe or the like in which the device is to operate, must extend throughout substantially the entire longitudinal portion of each segment which has the lateral wedge faces 47 and 48 thereon as this is the zone over which the complete seal between such pipe or the like and the body of this piston is maintained by these segments.

Furthermore, referring particularly to Fig. 3, it will be seen that the retainer rings 35 and 36 (ring 35 only being shown in this figure), have inward projections 49 adapted to extend between the endwise projections 31 and 32 on the segments so as to space them apart equally at all times and position them circumferentially with respect to each other thereby preventing them from becoming cocked in a circumferential direction. These spacing portions 49 are also formed with wedge shapes, the adjacent faces of any two segments being substantially parallel, so that they will permit free inward and outward movement of the segments without permitting substantially greater play of the segments in a lateral direction when they are radially inward than when they are radially in their outermost positions.

It is further noted that by the placement of the springs 20 and 21 and the arrangement of parts it is possible to provide springs which are relatively quite long with respect to the necessary degree of their expansion or contraction in the permissible radial movement of the segments. Hence, the forces exerted by these springs when the segments are in their fartherest out position with respect to the body will not be greatly diiferent from 8 the forces exerted by these spring whenthe segments are intheir innermost positions withrespect to the body. This; is highly desirable and is impossible in those cases in which springs are employed which act directly radially upon the segments as has been the case with some attempts to provide a suitable packer in the past.

' As will be seen in Fig. 5, the ends of the packer components in the assembly are not even. It will be noted that the ends 32 project further than the ends 31. The entire assembly is free to move axially on the body, limited only by the rings 35 and 36. When the expanded assembly moves endwise, the ends 32 will first be stopped by contact with an end ring while the other ends 31 will be free to move a little further. This latter overtravel, if continued, would serve to free the sealing surfaces 47 from 48. The advantage of this tendency is apparent if one assumes that the whole arrangement is moving through a pipe bore with the axial motivating force being applied to'the body while every segment of the whole packer assembly tends to drag, due to friction with the pipe walls, causing one set of ends 32 to bear against one or the other of the end rings 35 or 36. With the arrangement here provided, the tendency for the ends 31 at the same end of the assembly to continue to move causes a tendency for the faces 47 and 48 to part, reduces the radial force on the segments, reduces their friction against the pipe, and thereby reduces the tendency of ends 31 to continue to move. This tendency to continue to move is counteracted by the spring. In practice, the seal faces 47 and 48 do not actually separate and the thrust of the springs, by this mechanism of forces, is differentially distributed between the maintenance of the contact seal between faces 47 and 48 and the maintenance of radial thrust against the inside walls of the pipe. Thereby, the segments will be maintained in sealing position but will exert a minimum of frictional resistance to movement through a pipe.

From the foregoing it will be seen that in operation each of the packer segments being free to move within limits in a radially outward direction throughout its entire length, and being urged in such direction by balanced forces, each such segment will come into contact with the adjacent pipe wall or the like throughout substantially the entire length of that portion which is shaped to the contour of such pipe wall, and there will be no tendency toward tilting or cocking of the segments and hence no uneven wear on the faces of the segments which engage the pipe or the like.'

In Fig. 8 the arrangement is slightly difierent in that each segment is engaged only with the double wedge ring 112, sealed to the body 111 by an O-ring 113 and having upper and lower wedge surfaces 114 and 115, the single wedge rings having been omitted. Each segment is urged endwise in a direction to cause it to be expanded by the wedge ring, by means of a separate urging means such as the flat spring extending longitudinally of body 111. Each such spring is anchored to body 111 by suitable means such as by having one of its ends fixed to an anchor ring 117, anchored against axial movement along body 111 by a stop ring 119. The opposite end of each spring 120 is disposed in a hole provided therefor in the segment which the spring acts upon.

In this instance, each segment is urged outwardly at only one point but is urged bodily outwardly so that its entire outer surface will be seated against the inside of a pipe in which the device may be operating.

From the foregoing it will be seen that a means has been provided for accomplishing all of the objects and advantages of this invention.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects herein above set forth, together with other advantages which are obvious and which are inherent to the apparatus.

It will be understood that certain features and sub- 9 combinations'ar'e of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1s:

1. A piston comprising an elongated body, a plurality of longitudinally extending segments arranged in sideby-side relationship about said body and together completely encompassing the same and each having an outer surface of substantial longitudinal extent shaped to conform to the inner wall of a tubing, each of said segments being mounted for free radially outward movement throughout its length within limits, and means for urging each of said segments bodily radially outwardly simultaneously with balanced forces applied at longitudinally spaced points.

2. A piston comprising an elongated body, a plurality of longitudinally extending segments arranged in sideby-side relation about said body and together completely encompassing the same and each having an outer surface of substantial longitudinal extent shaped to conform to the inner wall of a tubing, each of said-segments being mounted for free radially outward movement throughout its length within limits, and means for urging said segments radially outwardly simultaneously, the means acting on alternate segments being balanced against the means acting. on-the' other segments.

3. A piston comprising an elongated body, a plurality of longitudinally extending segments arranged in sideby-side relationshihp about said body and together completely encompassing the same and each having an outer surface of substantial longitudinal extent shaped to conform to the inner wall of a tubing, each of said segments being mounted for free radially outward movement throughout its length within limits, and means for urging each of said segments radially outwardly simultaneously, the means acting on alternate segments being common to all of said alternate segments and the means acting on the other alternate segments being common to all of said other alternate segments, and said two means acting on the respective sets of alternate segments being balanced against each other to provide balanced forces acting on all the segments to expand them.

4. A piston comprising an elongated body, a plurality of longitudinally extending segments arranged in side-byside relationship about said body and together completely encompassing the same and each having an outer surface of substantial longitudinal extent shaped to conform to the inner wall of a tubing, each of said segments being mounted for free radially outward movement throughout its length within limits, each of said segments having lateral wedge surfaces engaging the lateral wedge surfaces of adjacent segments with such wedge surfaces on each segment converging in a longitudinal direction opposite to those on adjacent segments whereby opposite longitudinal movement of alternate segments will increase or decrease their aggregate circumferential extent, and means for urging each of said segments radially outwardly simultaneously, and for urging said segments at the same time in the longitudinal direction of convergence of said wedge surfaces to increase the aggregate circumferential extent of said segments.

5. A piston in accordance with claim 4 in which the outer surfaces of the segments which are shaped to conform to a tubing inner surface include that portion of each segment having lateral wedge surfaces.

6. A piston in accordance with claim 4 in which the means for urging said segments radially outwardly applies balanced forces to each segment at longitudinally spaced points and the outer surfaces thfat are. shaped t g f to a tubing inner surface include-that portion of eachsegmcnt having lateral wedge surfaces and extend therefrom toward one of said longitudinally spaced points at which one ofsaid balanced forces is applied.

7. A. piston in accordancewith claim. 4 in which the means for urging said segments radially outwardly applies balanced forces to each segment at longitudinally spaced points and one of the longitudinally spaced points to which the balanced forces are applied' on each segment falls within the longitudinal extent'of the lateral wedge surfaces on said segment.

8. A piston in accordance with claim 4 in which the means for urging each of the segments radially'outwardly includes a double wedge ring on said body within said segments and within the longitudinal extent of said lateral wedge surfaces, a wedge surface on the inner surface of each segment engaging said doublewedge ring and facing in the direction ofconvergence of the lateral wedge surfaces on the same seme'nt, and means urging said segments respectively in the direction of said convergence.

9. A piston in accordance with claim 4 in which the means for urging each of said segments radially outwardly includes a double wedge ring on the body within said segments and within the longitudinal extent of said lateral wedge surfaces, a wedge surface on the inner surface of each segment engaging said double wedge ring and facing in the direction of convergence'of the lateral wedge surfaces on the same segment, and a second wedge surface on each segment spaced from and oppositely inclined to the wedge surface engaging; said double wedge ring, a wedge member movable against said second wedge surface to force said segment longitudinally and radially outwardly, and a driver for driving. said Wedge member against said. second wedge surface.

10. A piston in accordance with claim 9 in which said driver is an initially distorted resilient member.

11. A piston in accordance with claim 4 in which the means for urging each of said segments radially outwardly includes a double wedge ring on said body within said segments and within the longitudinal extent of said lateral wedge surfaces, a wedge surface on the inner surface of each segment engaging said ring and facing in the direction of convergence of the lateral wedge surfaces on the same segment, a second wedge surface on each segment spaced from and oppositely inclined to the wedge surface engaging said double wedge ring, a wedge ring movable against said second wedge surfaces on each of alternate ones of said segments and another wedge ring movable against said second wedge surfaces on each of the other alternate ones of said segments, and resilient means urging each of said wedge rings against said second wedge surfaces, respectively.

12. In a free piston having a body and a metal seal comprising intermeshing seal segments extending longitudinally of the body and overlying a wedge ring to be expanded radially by engagement with said wedge ring upon longitudinal movement of alternate ones of said segments in opposite directions, the improvement which comprises means mounting said segments for free radial movement throughout their lengths and longitudinal movements on said body, both movements within limits, and means engaging each of said segments and urging it in a longitudinal direction to cause it to be expanded by said wedge ring.

13. In a free piston having a body and a metal seal comprising intermeshing seal segments extending longitudinally of the body and overlying a wedge ring to be expanded radially by engagement with said wedge ring upon longitudinal movement of alternate ones of said segments in opposite directions, the improvement which comprises means mounting said segments for free radial movement throughout their lengths and longitudinal movements on said body, both movements within limits, and separate means engaging each of said segments and 11 urging it in a longitudinal direction to cause it to be expanded by said wedge ring. 7

14. In a free piston having a body and a metal seal comprising inter-meshing seal segments extending longitudinally of the body and overlying a wedge ring to be expanded radially by engagement with said wedge ring upon longitudinal movement of alternate ones of said segments in opposite directions, the improvement which comprises means mounting said segments for free radial movement throughout their lengths and longitudinal movements on said body, both movements within limits, and means engaging each of said segments at a point spaced from said wedge ring and urging it simultaneously in a longitudinaldirection to cause it to be expanded by said wedge ring and in a radial direction at the point spaced from said wedge ring.

15. In a free piston having a body and a metal seal comprising intermeshing seal segments extending longitudinally of the body and overlying a wedge ring to be expanded radially by engagement with said wedge ring upon longitudinal movement of alternate ones of said segments in opposite directions, the improvement which comprises means mounting said segments for free radial and longitudinal movements on said body within limits, and means engaging each of said segments at a point spaced from said wedge ring and urging it simultaneously in a longitudinal direction to cause it to be expanded by said wedge ring and in a radial direction at the point spaced from said wedge ring, said last-mentioned means including two resilient members each urging a group of alternate ones of said segments in a longitudinal direction opposite to the other.

16. In a free piston having a body and a metal seal comprising intermeshing seal segments extending longitudinally of the body and overlying a wedge ring to be expanded radially by engagement with said wedge ring upon longitudinal movement of alternate ones of said segments in opposite directions, the improvement which comprises means mounting said segments for free radial and longitudinal movements on said body within limits,

and means engaging each of said segments at a point spaced from said wedge ring and urging it simultaneously in a longitudinal direction to cause it to be expanded by said wedge ring and in a radial direction at the said point spaced from said wedge ring, said last-mentioned means including two resilient members on opposite sides of said Wedge ring, each urging a group of alternate ones of said segments in a longitudinal direction opposite to the other.

17. In a free piston having a body and a metal seal comprising intermeshing seal segments extending longitudinally of the body and overlying a wedge ring sealed to and longitudinally movable with respect to the body to be expanded radially by engagement of said segments with said wedge ring upon axial movement in opposite directions of altenrate ones of the segments, the improvement which comprises means mounting said segments for free bodily radial and longitudinal movements on said body within limits, said last-mentioned means including axial movement limit stops positioned upon movement of the expanded assembly in one direction along the body to engage and stop movement along the body of only those segments moving in a direction to tighten them against the other segments while leaving said other segments free to continue movement along the body.

References Cited in the file of this patent UNITED STATES PATENTS 2,684,633 Knox July 27, 1954 

